Radiolysis of Chromatin Extracted from Cultured Mammalian Cells: Production of Alkali-labile Strand Damage in DNA

Publisher Website
Google Scholar
Abstract
Chromatin was isolated from cultured Chinese-hamster lung fibroblasts as an expanded aqueous gel. The DNA in isolated chromatin was examined by sedimentation on alkaline sucrose gradients. The average MW of the DNA was determined to be 50 million. .gamma.-Irradiation of isolated chromatin degraded the DNA to lower MW. The yield of single-strand breaks in the DNA was 0.02 single-strand breaks/krad-106 dalton, calculated from a dose-range of 1-400 krad and covering a DNA MW range of 2 .times. 107-1 .cntdot. 4 .times. 105. There was a considerable difference in efficiency of the formation of single-strand breaks in DNA irradiated as isolated chromatin compared with chromatin irradiated in whole cells before isolation. For isolated chromatin, values of 6 eV per break were calculated compared with about 8 eV/break for chromatin irradiated in whole cells, which suggested a large contribution from indirect action by aqueous radicals in isolated chromatin.